In the first experiment at Düsseldorf [1]} six HFS transitions were measured. Three of them belong to the manifold of the same spin structure and different coupling with orbital angular momentum \(N\) . Thus the weighted sum of the three states
\(\nu _{\rm spin} = \frac{1}{15}\sum _{F=1}^3(2F+1)f^{\rm exp}(122\rightarrow 12F)-f^{\rm exp}_{\rm spin-av}\) 
